Electrical signal repeating system



April 23, 1940. E. E. KLEINSCHMIDT El AL ELECTRICAL SIGNAL REPEATINQ SYSTEM Original Filed Dec. 13, 1929 ORNEY.

' INVENTOR.

EDWARD E. KLEINSCHMIDT DAVID S. HULFISH Patented Apr. 23,1940

UNITED STATES PATENT OFFICE 2,198,344 ELECTRICAL SIGNAL REPEATING SYSTEM Edward E. Kleinschmidt, Highland Park, and

David S. Hulflsh, C Teletype Corporation tion of Delaware I hicago, Ill., assignors to Chicago, 11]., a corpora- Original application December 13, 1929, Serial No. 413,838, now Patent No. 2,153,574, dated April 11, 1939. Divided and this application May 20,

1938, Serial No. 208,9

' 18 Claims.

exchange system adaptable for combined service,

alternatively telegraphic or telephonic communication.

Telegraph signals'are characterized by direct currents interrupted in code manner to form spacing and marking signal impulses, while telephone signals are characterized by a variable current varying in voice frequencies. Specially designed equipment is required for permitting both telegraph and telephone communication over a single circuit and through conventional automatic telephone switching circuits and apparatus.

Automatic telephone switching systems are operated by dialed signal impulses of direct current to which the switching equipment responds to effect connection with a called line. Maintenance of an established connection is ordinarily controlled by preserving a direct or holding current through the calling substation. Re- 25 lease of the equipment is accomplished by discontinuance of the direct current for a predetermined interval.

A complete system for rendering telegraph and telephone service alternatively from an integral a switching equipment in which switches are common to both services is disclosed and claimed in a copending application Serial No. 413,338 filed December 13, 1929, patented 'April 11, 1939, No. 2,153,574, by E. E. Kleinschmidt and D. S. Hulfish of which application the present application is a division, specifically with reference to the telegraph repeating circuits and devices dis closed in the original application.

In general, the present invention contemplates a directory number or combination of signal codes identifying severally each telegraph set in a combined telegraph and telephone exchange system having automatic apparatus such that, when such a telegraph, directory number is dialed, the automatic equipment will operate to set up a communicative connection including telegraph translating and repeating equipment. After the connection has been completed through to the called substation, apparatus at the calling end of the connection will translate direct current signals originated at the calling substation into alternating currents substantially of voice frequency, and apparatus at the called end of the connection will retranslate the alternatu= ing currents into direct current signal impulses for operating the telegraph receiving apparatus. Provision is made for permitting telegraph signaling in both directions following establishment of a connection, and for restoration of the switching equipment at the end of communication.

The main object of the present invention is the provision of a single repeating device which is capable of effecting the functions incident to maintaining an established connection and to telegraphing between the connected stations.

It is a feature of the complete system of the invention of the parent application that a connection may be established from a substation of one central oflice to a trunk line extending to another central oflice, and thence extended to a substation of the second mentioned central office, automatic switches being operated in both central offices under control of the first mentioned substation.

It is a feature of the invention of the parent application that automatic switches shall be operated to establish a telegraph connection exactly as they are operated to establish a telephone connection; namely, by impulses of direct current. It follows that when establishing a connection for telegraph communication, it is required to repeat signals of direct current over the trunk circuit to control selective adjustment, then to maintain an effected adjustment, and to control subsequent disconnection of switches, and concurrently, while communicating telegraphically, it is required to repeat telegraph signals comprising currents of voice frequency over the trunk circuit.

A connection may be established for telephone communication or a different connection may be established for telegraph communication using the same subscriber lines'and some of the same central office equipment.

A better understanding of the invention may be had from the following description, taken in conjunction with disclosures of the parent application and with the accompanying drawing wherein:

Fig. 1 is a diagrammatic showing of unoper ated switches and circuits for forming a proposed communication circuit from a calling to a called substation shown before switching connections have been made;

I Fig. 2 is a circuit diagram showing the completed circuit connections with a marking signal condition between a calling substation and a called substation for telegraph communication; Fig. 3 is a circuit diagram of a selector; and Fig. 4 illustrates a modified circuit embodying the principles of the repeater system of the invention.

Referring to Figs. 1 and 2, two substations I and 2, remote from each other, are shown, each station being provided with a telegraph set and optionally with a telephone set also. Extending from each of the substations are their individual signaling lines 3, 4 and 5, 8, respectively, over which telegraph communication may be carried on subsequent to the dialing of a telegraph directory number.

The signaling line 3, 4 extends to the rotary line switch 1,.which is of well-known construction and which, in response to closure of the circuit loop at the substation, operates automatically to find an idle selector 8, the controlling circuits of which are connected over conductor 8 to a bank contact in rotary switch 1.

After seizure of switch 8 by operation of nonnumerical switch 1, an operator at station I may dial 768,644 to control switches 8, I2, 28, 31, 38 to establish a telephone connection with station 2, or may dial 8,768,855 to control switches 8, I8, I2, 28, 31. 53 to establish a telegraph connection with station 2.

Selector 8, which also is of well-known construction, operates in response to the first dialing signal or digit signal 8 from substation I, to adjust the wipers of the switch 8 vertically to a selected position with reference to its bank contacts, as illustrated by upper dotted line, after which the wipers of the switch 8 rotate to engage an idle junction circuit I3 extending to a repeater relay set I 4, which is arranged to receive impulses of direct current from substation I and to retransmit signals of direct current for switch control as well as signals of voice frequency for telegraph transmission purposes.

Upon seizure of the repeater set I4 by switch 8, the substation I is connected conductively to the repeating relay 23, which becomes energized, and its armature 24; through inductance 25, controls a rotary switch I5 of construction similar to the line switch 1, which operates to connect with an idle selector I8. Relay 23 remains energized over a circuit closed through a dialing transmitter at substation I.

Upon dialing of a second directory digit, each break of the dial at substation I releases the armature of the repeating relay 23, which interrupts direct current from switch I8 flowing through armature 24 and inductance 25, and substitutes an alternating current of voice frequency originated in induction coil 3|. There is in the circuit of this alternating current at this time, no apparatus responsive thereto, and accordingly, the alternating current is without effect. However, each break of the contact of armature 24 operates the switch I8 selectively and positions its wipers, as indicated by dotted line, to select an idle selector I2. Similarly, the dial signal im-'- pulses of the third directory digit at substation I are repeated by repeater I4 to the selector switch I2, and-an idle junction circuit is selected which will extend the circuit of armature 24 to an idle selector 28. Fourth dialing impulses are effective to operate the selector switch 28, fifth dialing impulses for 8 are effective to operate a selector switch 31, and sixth and seventh dialing impulses closed a circuit for direct current through inductance 25, and in response to open-circuit controlling condition at substation I, has closed the circuit through inductance coil 3I to supply current of voice frequency which has been futile because the circuits to which the voice frequency currents have been applied have not included any device responsive to currents of voice frequency.

Upon connecting with the called line, relay 342 is energized, as shown in Fig. 3, to close its contacts in the circuit of secondary winding of induction coil 48, and repeating relay 48 is energized to control the energizing circuit of relay 45, which is responsive to currents of voice frequency, thus completing the circuits of the tele-,

graph repeating system.

Referring more particularly to Fig. 2, the circuits of the repeating system may be traced in three line sections. First or originating line section extends from grounded battery, through a winding of relay 23, a conductor I3, switches '8 and 1, conductor 4, key 14, permutation transmitter 81, recorder magnet 88, returning over key 14, conductor 3, switches 1 and 8, a conduc tor I3, and a winding of relay 23 to ground. Second or terminating line section extends from grounded battery, through a winding of relay 48, contacts of switch 53, line conductor 5, contacts of relay 318, winding of relay 383, recorder magnet 394, and permutation transmitter 385, returning over contacts of switch 318, line conductor 8, contacts of switch 53, and a winding of relay 48 to ground.

Third or intermediate linesection extends, for transmitting from substation I, from secondary winding of induction coil 3 I, whose primary winding is indicated as a source of alternating current of voice frequency, through condenser and back contact of armature 24 when repeating relay 23 is deenergized, through contacts of switches I5, I8, I2,'28, and 31, armature 41 and front cont-act, condenser 44 and signal-receiving relay 45 responsive to currents of voice frequency, returning to induction coil 3I over parallel wiring in. the several switches. A marking signal in the repeating system is constituted by a condition of current in the first and third line sections, energizing both relays 23 and 48 and holding open the back contacts of both armatures 24 and 41, thus holding open the circuits of both induction coils 3 I and 48 with no voice frequency current in the intermediate line section, but with a closed circuit carrying direct current in the intermediate line section fromgrounded' battery, through a winding of relay 43, contacts of automatic switches 31, 28, I2, I8, I5, contact of energized relay 23, and inductance 25, returning through Functions of repeater I4 in the process of establishing a telegraph communicative connection are solely to retransmit signals which are of direct current nature, but when the connection has been established and the alternating current voice frequency relay 45 has been included in the communicative connection, the functions of the repeater I4 are increased to the double requirement, first, receiving direct current signal spacing impulses of telegraph communication nature and retransmitting each such received impulse of contacts of the automatic switches and a winding of relay 43 to ground. I

spacing nature in the form of a time period of alternating current voice frequency effective upon alternating current frequency relay 45, and second, receiving direct current signal marking impulses of switch-controlling nature and retransmitting each such received impulse in the form of a repeated'cirect current impulse effective upon the relay 43 to energize the relay 43 for purposes of holding the flnalconnector switch and other switches of the connection in communicative condition.

The method of operating relay 43 to eifect maintenance of an established connection comprises the steps-of energizing relay 43 in response to a closed circuit condition corresponding to a telegraph marking signal at the calling substation, deenergizing relay 43 in response to an open-circuit condition corresponding to a telegraph spacing signal at the calling substation I, maintaining a maximum length of spacing signal during telegraph communication below a predetermined time value, and effecting discontinuance of the said established connection in response to a spacing signal at substation I wh ch exceeds the said predetermined time period. Apparatus to this end is illustrated in Fig. 3 which shows pertinent elements copied from Fig. 6 of theparent application.

Referring to Fig. 2, relay 4II being inactive, the relay 23 responds to signaling conditions in permutation transmitter 81 at substation I, and relay 43 is wholly controlled by armature and front contact of relay 23, being therefore indirectly controlled by the transmitter 81. The aforesaid time period is determined by adjustment of the time element in slow-to-release relay 326, Fig. 3.

Discontinuance of the established connection is effected by deenergization of relay 362 permitting armatures 313 and 386 to disconnect the line conductors 5, 6 from the winding of relay 48. Denergization of relay 362 is effected in response to a spacing impulse generated at substation I and having a time value greater than the aforesaid time period. At substation I, Fig. 2, switch 14 is reversed by manual control, thus opening the energizing circuit of relay 23. Deenergization of relay 23 by its front contact opens the energizing circuit of relay 43. Deenergization of relay 43, Fig. 3, opens the energizing circuit of slow-to-release relay 326, which is the starting condition for the predetermined time period. At expiration of the predetermined time period, relay 326 releases its armature 328, which interrupts the holding circuit for relay 362. Armatures 313 and 386 are released and opening of their contacts interrupts the connection of line conductors 6 and 6.

Throughout the duration of telegraph communication in an established connection. armature 24 and front contact in relay 23 are utilized continuously in vibratory manner to control circuits and apparatus local to the central office to maintain the switches of the connection in their adjusted position. To effect transmission of significant telegraph signals by use 01' the same repeating relay 23, a back contact is provided for armature 24 and a telegraph communication circuit is provided including secondary winding of an induction coil 3| as a source of alternating-current voice-frequency en- Alternating current from induction coil 3| is received as a signal of spacing nature by relay 45 which operates the armature to connect together the line conductors 5, 6 through branching local conductors 98 and 99, thus shunting the substation receiving magnet 394 which, by deenergization, manifests the signal of spacing na-- ture generated by transmitter 81 and repeated first by relay 23 and again by relay 45.

Reflection estoppel is effected by a circuit including battery, upper Winding of relay 48, local conductor 98, contact and armature 5| of energized relay 45, local conductor 99 and lower'winding of relay 48 to ground return, holding energized the repeating relay 48 throughout the duration of a spacing signal originated by transmitter 81.

embodying the invention in simplified form.

A first line section includes battery I00, winding oi. repeating relay IOI,.line conductor I02, winding of substation relay I03, contacts of transmitting key I04 and ground return, with a shunting path through local conductor I05 and open armature I06 of relay I01 and contact to ground. forming a closed telegraph circuit energized by battery I00 and controlled either by key I04 to open the circuit to deprive both relays |0I and I03 of energy, or by armature I06 and contact to form a shunt around the winding of relay I03,

depriving relay I03 of current but maintaining current in the winding of repeater relay IOI.

A second and similar line section includes battery I 20, relay I2l, line conductor I22, relay I 23, key I24, local conductor I25, armature I 26, and relay I21.

A third line section I08 is without current or in open-circuit condition representing a marking telegraph signal condition. A circuit through conductor I08 may be closed by armature I09 when released, including battery IIO, back contact and armature I09, conductor I08, armature I29 and front contact, Winding of relay I21 and ground return, or, alternatively, by armature I29 when released, including battery I30, back contact and armature I29, conductor I08, armature I09 and front contact, winding of relay I01 and ground return.

Two methods of working telegraph circuits; namely, the open and closed circuit methods, are Well known. The open circuit method is almost exclusively employed in England, whereas the closed circuit method is in most extensive use in the United States. A circuit worked upon the open method is one in which no current traverses the circuit when idle, and, as a corollary, batteries are required at both ends of the circuit. For further details on these methods, reference should be made to Telegraphy, Herbert, London, Whittaker & Company, 1906. The term open circuit used in the claims hereof is to be in accordance with the foregoing definition.

Fig. 4 illustrates a telegraph repeater system In operation, a signal of marking nature is constituted by the condition shown in Fig. 4 with relays I03, I23 energized at terminal stations and with relays IOI, I2I energized at a repeating station. A signal of spacing nature is propagated by opening key I04, deenergizing the home relay I03, and the repeating relay IOI, releasing the armature I09 which closes a circuit over conductor I08 to energize the relay I21 and to attract armature I26 which shunts-the winding of relay I23, deenergizes relay I23 and reproduces in relay I23 the signal condition initiated by key I 04. Reflection estoppel is eifec'ted by a circuit including battery I20, winding of relay I 2|, armature I26 and contact and ground return which holds repeating relay i2i energized throughout the duration of spacing signal originated by key IM.

Two species of embodiments of the invention have been illustrated herein, and it is obvious that further species will result in applying the invention to variant systems of telegraph apparatus by one skilled in the art to which the invention pertains.

What is claimed is:

l. The method of transmitting telegraph intelligence from a point oi. origin to a remote point which comprises the steps of establishing a communicative telegraph connection between said two points under control of the point of origin, and thereafter transmitting in alternation under control of said point of origin currents for maintaining said established connection and currents constituting transmission oi' intelligence.

2. The method of -transmitting telegraph intelligence from a point of origin to a remote point which comprises the steps of establishing a communicative telegraph connection between said two points under control of the point of origin, thereafter transmitting in alternation under control of said point of origin currents for maintaining said established connection and currents constituting transmission of intelligence, and eifectingi, discontinuance of said telegraph con-- nection by discontinuing said maintaining currents.

3. The method of transmitting telegraph intelligence from a point of origin to a remote point through two intermediate points which comprises the steps of establishing a communicative telegraph connection from said point of origin through first and second intermediate points to said remote point, thereafter transmitting intelligence signals from said point of origin to said first intermediate point, repeating said intelligence signals and generating currents for maintaining said established connection, transmitting said repeated intelligence signals and said maintaining currents in alternation between said flrst intermediate point and said second intermediate point, repeating said intelligence signals at said second intermediate point, and retransmitting said last mentioned repeated signals to said remote point.

4. The method of transmitting telegraph intelligence between a point of origin and a remote point through two intermediate points which comprises the steps of establishing a communicative telegraph connection from said point of origin through first and second intermediate points to said remote point, thereafter maintaining said established connection under control from said point of origin while transmitting intelligence signals by direct current signals from said remote point to said second intermediate 'point, repeating said signals and retransmitting from said second to said first intermediate point,

again repeating said signals, and retransmitting by direct current signals from said first intermediate point to said point of origin.

5. The method of transmitting telegraph intelligence between a point of origin and a re- 'mote point through two intermediate points which comprises the steps of establishing a communicative telegraph connection from said point of origin through first and second intermediate points to said remote point, thereafter maintaining said established connection by continuous direct current between said first and second intermediate points under control from said point oi! origin while transmitting intelligence signals -by direct current signals from said remote point to said second intermediate point, repeating said intelligence signals and converting into alternating currents and retransmitting from said second to said first intermediate point over the conductors carrying the connection-maintaining direct current, again repeating said intelligence signals and converting into direct current signals, and retransmitting by.direct current signals from said first intermediate point to said point of origin.

6. In a telegraph repeating system, means for establishing a communicative telegraph connection between two stations, means for transmitting direct current signals in alternation with alternating current signals were portion of said established connection, means responsive to said direct current signals and eflective to maintain said connection, and repeating means responsive to said alternating current signals and effective to convert said alternating current signals into direct current signals and to retransmit the direct current signals.

7. In a telegraph repeating system, means for establishing a communicative telegraph connection from a first station through first and second intermediate switching points to a second station, means to transmit direct current signals from said first station to said first switching point, means to repeat said signals and to convert said signals into alternating current signals, means to transmit said alternating current signals from said firstto said second switching point, and means to repeat said signals and to convert said alternating current signals into direct current signals-and to transmit said direct current signals from said second switching point to said second station.

8. In a telegraph repeating system, means for establishing a communicative telegraph connection from a first station through first and second intermediate switching points to a second station, means to transmit direct current signals from said first station to said first switching point, means to repeat said signals and to convert said signals into alternating current signals, means to transmit said alternating current signals from said first to said second switching point, means to repeat said signals and to convert said alternating current signals into direct current signals and to transmit said direct current signals from said second switching point to said second station, and means at said first switching point to generate connection-maintaining signals and to transmit said maintaining signals alternately with said alternating current signals.

9. In a telegraph repeater system, a repeating relay responsive to direct current code signals and having front and back contacts, a circuit including a source of direct current, one of said contacts and a relay responsive to direct current, and a further circuit including a source of alternating current, the other of said contacts and a further repeating relay responsive to alternating current.

10. In a telegraph repeater system, line-switching means, a repeating relay responsive to direct current code signals and having front and back repeating contacts, a circuit including a source of trol said line-switching means, and a further circuit including a source of alternating current, the other of said contacts and a further repeating relay responsive to alternating current.

11. In combination, two stations,,a central office through which said stations may be connected, switching mechanism including a telegraph repeater in the central oiiice, means for connecting said stations through said central oflice, and additional means for connecting said stations, said additional means including said switching mechanism with the telegraph repeater.

12. In combination, two stations, a central otfice through which said stations may be connected, switching mechanism including a telegraph repeater in the central ofllce, means for connecting said stations through said central office, additional means for connecting said stations, said additional means including said switching mechanism with said telegraph repeater, and means whereby the dialing of the directory number determines which of the two said means shall be included in the connection.

13. In combination, a first station, a second station, a first path between the two stations, a second path between the two stations, said second path including telegraph repeating mechanism, and means at each station for selecting either one of the paths to the other station and establishing a connection therethrough.

14. In a telegraph repeater, a closed circuit line, an open circuit line, and means comprising a set of telegraph repeating relays associated with said lines and adapted to reproduce in each line the telegraph signals originating in the other line.

15. In a telegraph repeater system, two telegraph stations, two repeating stations, a closed circuit line connecting each of the telegraph stations with one of the repeating stations, and an open circuit telegraph line connecting the two repeater stations to each other.

16. In a telegraph repeating system, a plurality of closed circuit lines, an open circuit line, repeating relays controlled by said closed circuit lines to repeat signals into said open circuit line, and further repeating relays controlled by said open circuit line to repeat signals into one of said closed circuit lines.

17. In a telegraph repeating system, a plurality of closed circuit lines, an open circuit line, repeating relays having windings connected to said closed circuit lines and having contacts connected to said open circuit line, and further repeating relays having windings connected to said open circuit line and having contacts connected to said closed circuit lines.

18. In a telegraph repeater system, a first closed circuit line section, a second closed circuit line section, and means to repeat signals from one of said line sections into other 01. said line sections, said means comprising relays and an 80 

